“We switched from IV saline to PlasmaLyte, and then that became an issue as well,” said Dr. Michael O’Neal, Vanderbilt manager of pharmaceutical procurement. “Then we switched to saline again, and now we’re in a kind of hybrid mode. It’s like squeezing a balloon: You close one pressure point and another one pops open.”

The U.S. Food and Drug Administration is working with three saline manufacturers to ease the shortage, hoping to return production to normal by the second quarter of 2014.

Saline is just the latest in a series of medicine shortages. Dr. Michael Christensen, a parenteral (non-oral) nutritionist who works mainly with infants at Le Bonheur Children’s Hospital in Memphis, said almost every medicine he uses has been in short supply sometime in the past few years.

“It takes the fun out of caring for patients,” said Christensen, who also works at the University of Tennessee Health Science Center. “You have to allocate resources for those who need it. You have to figure out how to stretch out supply, especially for vulnerable patients.”

Nashville hospitals have responded to the shortage by monitoring and altering their use of IV fluids.